Ammonium Iodide is the chemical compound NH4I. It is used in photographic chemicals and some medications.[1] It can be prepared by the action of hydroiodic acid on AMMONIA. It is easily soluble in water, from which it crystallizes in cubes. It is also soluble in ethanol. It gradually turns yellow on standing in moist air, owing to decomposition with liberation of iodine.[1]
I have no horse in this race but the decomposition of Iodine compounds is very complex - way over my paygrade.
In the Iodine forum Ted was posting some interesting studies about iodo-mercuric compounds being formed and acting as pseudo chelator.